Technical Field
The present disclosure generally relates to electronic circuits and, more specifically, to capacitors having a value settable by application of a bias voltage. The present disclosure more specifically applies to BST (Barium-Strontium-Titanium) capacitors.
Description of the Related Art
BST capacitors have essentially been developed for radio applications, in particular for mobile telephony. Having a capacitor with an analogically-adjustable capacitance significantly improves the performance, since it enables to adapt the device comprising such a capacitor to the outer environment.
A BST capacitor appears in the form of an integrated circuit (this type of capacitor is also called adjustable integrated capacitor). The capacitance of a BST capacitor is set by the value of a D.C. bias potential which is applied thereto, generally in a range from a few volts to a few tens of volts, typically between 2 and 20 volts.
The bias voltage of a BST capacitor is generally provided by a dedicated control circuit, performing a high-voltage digital-to-analog conversion, that is, converting a digital configuration word (generally, a byte) into a D.C. analog voltage to be applied to the capacitor to set the capacitance thereof.
The reliability of a system using one or a plurality of BST capacitors depends on the reliability of the conversion of the set point value which may be affected by a drift in the matching between this set point value and the reached capacitance value.